Twenty years ago, they landed a licensing deal with Carolina Pad of Charlotte, N.C., for their Ghostline Poster Board that features a barely visible grid so that you can pull off projects without having to measure or draw lines.

Every three months, the 70-something sisters from Plano receive their latest 5 percent royalty installment on Ghostline sales that have totaled more than $300 million in the past two decades.

Now they want to help others make their millions and have spent countless hours giving free (but priceless) advice to entrepreneurial hopefuls. So who could be better to dispense a dose of reality-laced encouragement?

Since starting my "Ideas at Work" column in 1992, I figure I've profiled nearly 2,000 entrepreneurs, and the Russell sisters' story is one of my favorites because it's more than about mailbox cash flow.

Barb, 75, a one-time office administrator, and Mary, 70, a former schoolteacher, are Little Red Hens. No one wanted to help them. So they did it themselves.

"We call ourselves twins born five years apart because we think so much alike," Barb says, sitting in her living room with Mary. "We're pretty much interchangeable."

Mary Sarao, left, and Barbara Pitts, are shown next to Barbara's mailbox outside her home in Plano.

(Ben Torres/Special Contributor)

In 1995, Mary's ninth-grade daughter messed up a school project the night before it was due. That meant a 10 o'clock last-minute trek to Tom Thumb for another sheet of poster board.

Mary came home, pulled out a yardstick and drew fine lines so that the words and pictures wouldn't be whompyjawed. She went to bed grousing about there had to be a better solution.

It came to her that night in a dream.

The next morning, she called Barb and they set the wheels of invention into motion.

They wanted to license their product from the outset. They knew they didn't have enough market muscle to go up against the giant manufacturers in the office and school supply business.

"We discovered that there were five or six companies that distributed all of the poster board in the country," Mary says. "Plus paper and poster board is heavy, so shipping for us would have been a serious challenge."

One company contacted the sisters and said if they could prove that they'd filed for a patent for Ghostline, it would license the product.

After receiving their patent application with the specific details blacked out, that company went incommunicado.

A few months later, a friend called from the School Home Office Products Association trade show that was being held in Dallas that year. He told Barb that the company had ripped off their products.

Barb finagled her way into the show, found the booth, yanked down the displays, confiscated the rest of the product and walked out with the contraband.

"They were just standing there with their mouths open," Barb recalls. "They didn't know who I was. But I took everything they had. I called Mary in tears and said, 'We're ruined.'"

Ruination to salvation

Ruination turned into salvation. The vice president of new product development at Carolina Pad had seen the products before Barb seized them. That jogged his memory about the samples the sisters had sent.

"The president flew to Dallas, laid out all of their products in front of us and said, 'If you let us have your product, we'll sue that company the day your patent issues.'"

And that's what happened. What went around came around. The company helped push their combined royalty total to about $15 million, which they've shared with the taxman.

As a way to pay their good fortune forward, Barb and Mary operate a free website, asktheinventors.com, that is a treasure trove of how-to and what-not-to-do information amassed through their inventive journeys.

"It costs thousands of dollars to get a patent," Barb says. "Who has thousands of dollars for a patent? We learned you can do it a step at the time. It doesn't take a whole lot of upfront money as long as you pay for it as you go."

Mary and Barb don't receive a dime for the counsel they've dispensed to hundreds of thousands of wannabe inventors who've contacted them through their site in the past 17 years.

"In the earlier years, it took both of us several hours each day answering email," Barb says. "We finally developed some basic letters for the most commonly asked questions, which we personalized with some of our own remarks and that helped. Now it has tapered off enough that we alternate weeks answering the emails, and we each get several days off at a time."

Not surprisingly, the No. 1 and No. 2 questions are: "Where do I start?" and "How do I get money?" — not necessarily in that order.

Not resting on laurels

They've written three books: The Everything Inventions and Patents Book, Inventing on a Shoestring Budget and their latest, Mailbox Money! A Step-by-Step Guide to Licensing your Invention for Royalties.

"We get a lot of people who want us to develop and patent their ideas," Mary says. "We don't do that. We offer people resources, support and encouragement."

Barb and Mary are currently in the process of creating a library of YouTube videos for those who'd rather see it than read it.

"The website has been great. But we were discussing this one day, and I said, 'You know what, Barb, whenever I want to find out how to do something, I look it up on YouTube,'" says Mary.

"I have a little room in my house that's my sewing and junk room. And we put up a tablecloth on the wall, a table in front and a camera and made a studio. We sit down and talk about various topics."

Barb and Mary aren't resting on their lined-paper laurels.

Their latest trademarked and patent-pending product, FilmStar, is a star-shaped makeup applicator. One side is a cosmetic-quality sponge that cuts down on the amount of makeup you have to use. The other side is film that smoothes out the application.

Barb came up with the idea when she was applying makeup wearing rubber gloves that women use when they dye their hair, hoping to protect her manicured nails.

She was using a typical makeup sponge when it slipped out of her hand. In her rush, she smoothed out her makeup with her gloved hand.

"It was one of those lightbulb moments," Barb says. "The makeup was spreading gorgeously.

"I told Mary, 'You're not going to believe this. I don't like wearing a glove to do my makeup, but I love the way it works. It uses a tiny fraction of what I usually use. And it's flawless.'"

Mary went to work on prototypes, using cookie cutters and soap molds to make different shapes. They settled on a star because the tips fit into tiny corners of eyes and noses.

Even though FilmStar isn't on the market yet, Mary and Barb gave away hundreds of boxes to 10 women's shelters in the East Texas area. "We felt that it might help in some way to repair the damaged egos of abused women if they had a luxury item to apply makeup," Barb says.

Just another reason why these gals are two of my favorites.

Twitter: @CherylHall_DMN

Barb and Mary's nine steps before you step out

Stay within your area of expertise.

Find something you can implement. That doesn't mean that you have to know everything about how to make your invention right now. It just means that you have the ability to find out what you need to know in order to proceed with your invention.

Make sure your idea is yours to pursue.

Visit all the stores that might carry merchandise similar to your idea. Go to Amazon. Google a generic description of your idea. Check online catalogs. Your idea may be out there in limited distribution that you're not aware of. But if it is, you can't patent it.

Make sure your idea is one that a huge demographic wants.

If it isn't, you're going to go to a great deal of trouble and expense for something you can't sell. Is it something that people will consume and buy again? Is it something that is used by most of the population?

Do a preliminary patent search.

More than 97 percent of the patents issued to independent inventors never make it to the marketplace. But if they are patented, and the patent is still active, you would be infringing if you created that product. If your preliminary search doesn't turn up an existing patent, spend the $400 to $700 for a professional patent search before proceeding with an even more costly patent protection.

Develop a prototype.

It doesn't need to look like the finished product. Contact the engineering school of a local university to see if they can help.

Decide whether to manufacture and distribute or license.

Most retail outlets will not buy from a single-product vendor. If you license your product to a manufacturer with other products in stores, it is a simple matter to add your invention to its lines.

Determine what percentage of royalty is fair.

The most common royalty pays 5 percent but can range from 1 percent to 20-plus percent, depending on the item, the industry, the size of the potential market and the competition for your agreement between potential licensees.

Determine the product cost vs. the retail sales price.

Accurately estimate how much it will cost to make your product and multiply that by four. Then find out if people will actually pay that much for your product.

Be prepared for the long haul.

Inventing is not a fast process. It takes months, maybe years, to develop your prototype. You have to be ready for all the ups and downs.